kakz wrote:The ratio, by weight, of the four ingredients A, B, C, and D of a certain mixture is 4:7:8:12. The mixture will be changed so that the ratio of A to C is quadrupled and the ratio of A to D is decreased. The ratio of A to B will be held constant. If B will constitute 20% of the weight of the new mixture, by approximately what percent will the ratio of A to D be decreased?
(A)15%
(B)25%
(C)35%
(D)45%
(E)55%
Since A:C = 4:8, A:C quadrupled = 12:8 = 4:2.
A:B held constant = 4:7.
Thus, new A:B:C = 4:7:2.
Since B = 1/5 of the new mixture:
7 = (1/5)x.
x = 35.
Since x=35 and A+B+C = 4+7+2 = 13:
D = 35-13 = 22.
Old A : D = 4:12 = 1:3 = 11/33.
New A : D = 4:22 = 2:11 = 6/33.
Since old A : D and new A : D have the same denominator, we can determine the percent decrease using only the numerators:
(11-6)/11 * 100 = 500/11 ≈ 45.
The correct answer is
D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
